A car travels 690 km in 30 hours. What is its average speed (in km/h)?

Introduction / Context:
Average speed over a single uninterrupted leg equals distance divided by total time. Here, the numbers are chosen for a clean division.

Given Data / Assumptions:

• Distance = 690 km.
• Time = 30 h.

Concept / Approach:
Average speed = distance / time.

Step-by-Step Solution:
Average speed = 690 / 30 = 23 km/h.

Verification / Alternative check:
23 km/h * 30 h = 690 km, reconciling with the given distance.

Why Other Options Are Wrong:
25, 20, 18 km/h yield 750, 600, 540 km respectively over 30 h, not 690 km.

Common Pitfalls:
Mistyping the division or rounding unnecessarily when the quotient is exact.

Final Answer:
23 km/h